Multi-mode integrated starter-generator device with preloaded clutch

Abstract

A combination starter-generator device includes an electric machine and a gear set configured to receive rotational input from the electric machine and from the engine and to couple the electric machine and the engine in a first power flow direction and a second power flow direction. The gear set is configured to operate in one of multiple gear ratios in the first power flow direction and at least one gear ratio in the second power flow direction. The starter-generator device further includes a clutch arrangement with at least one active clutch selectively coupled to the gear set to effect the gear ratios in the first power flow direction and in the second power flow direction. The clutch arrangement further includes at least one drag clutch to apply a drag force on the gear set to slow the electric machine.

What is claimed is: 
     
       1. A combination starter-generator device for a work vehicle having an engine, the starter-generator device comprising:
 an electric machine; 
 a gear set configured to receive rotational input from the electric machine and from the engine and to couple the electric machine and the engine in a first power flow direction and a second power flow direction, the gear set configured to operate in one of multiple gear ratios in the first power flow direction and at least one gear ratio in the second power flow direction; and 
 a clutch arrangement with at least one active clutch selectively coupled to the gear set to effect the gear ratios in the first power flow direction and in the second power flow direction, 
 wherein the clutch arrangement further includes at least one drag clutch to apply a drag force on the gear set to slow the electric machine. 
 
     
     
       2. The combination starter-generator device of  claim 1 ,
 wherein the gear set includes an input shaft that receives the rotational input from the electric machine in the first power flow direction, and wherein the at least one drag clutch includes a first drag clutch portion mounted on the input shaft. 
 
     
     
       3. The combination starter-generator device of  claim 2 ,
 wherein the gear set includes an output element rotating with the engine, and 
 wherein the at least one drag clutch includes a second drag clutch portion mounted for rotation with the output element. 
 
     
     
       4. The combination starter-generator device of  claim 3 , wherein the gear set includes a ring gear as the output element and a ring gear cover mounted within the ring gear to at least partially enclose the gear set and rotating with the ring gear, the second drag clutch portion being mounted on the ring gear cover. 
     
     
       5. The combination starter-generator device of  claim 4 , wherein the first drag clutch portion includes a flange mounted to the input shaft and a shaft plate extending from the flange. 
     
     
       6. The combination starter-generator device of  claim 5 , wherein the second drag clutch portion includes at least one cover plate extending from the ring gear cover, the shaft plate frictionally engaging the at least one cover plate to apply the drag force. 
     
     
       7. The combination starter-generator device of  claim 6 , wherein the drag force is approximately 10 Nm. 
     
     
       8. The combination starter-generator device of  claim 7 , wherein the at least one drag clutch is spring loaded to passively apply the drag force on the input shaft. 
     
     
       9. The combination starter-generator device of  claim 6 ,
 wherein the gear set is configured to operate in one of at least a first gear ratio, a second gear ratio, and a third gear ratio in the first power flow direction and at least a fourth gear ratio in the second power flow direction, and 
 wherein the at least one drag clutch is configured to slow the electric machine during transitions between the first, second, and third gear ratios and between the first power flow direction and the second power flow direction. 
 
     
     
       10. The combination starter-generator device of  claim 9 ,
 wherein the clutch arrangement is a dog clutch arrangement selectively coupled to the gear set to effect the first, second, and third gear ratios in the first power flow direction and the fourth gear ratio in the second power flow direction, and 
 wherein the combination starter-generator device further comprises a cam plate configured to shift the at least one active clutch from a disengaged position in which the at least one active clutch is decoupled from the gear set into an engaged position in which the at least one active clutch is coupled to the gear set. 
 
     
     
       11. The combination starter-generator device of  claim 10 ,
 wherein the at least one active clutch includes at least a first clutch, a second clutch, and a third clutch, each selectively repositionable between the engaged position and the disengaged position, 
 wherein the first, second, and third clutches are ring-shaped with the second clutch concentrically arranged within the first clutch when both of the first and second clutches are in the disengaged positions and the third clutch concentrically arranged within the second clutch when both of the second and third clutches are in the disengaged positions, and 
 wherein the cam plate is generally disc-shaped with a first face and a second face, the cam plate including a plurality of cam teeth extending from the first face to engage with and shift the first, second, and third clutches from the disengaged positions to the engaged positions. 
 
     
     
       12. The combination starter-generator device of  claim 11 , wherein the cam plate is configured to be pivoted through a range of angular positions, wherein, at a first angular position, the at least one first cam tooth engages the first clutch and the second and third clutches remain disengaged relative to the at least one second cam tooth and the at least one third cam tooth, wherein at a second angular position, the at least one second cam tooth engages the second clutch and the first and third clutches remain disengaged relative to the at least one first cam tooth and the at least one third cam tooth, and wherein, at a third angular position, the at least one third cam tooth engages the third clutch and the first and second clutches remain disengaged relative to the at least one first cam tooth and the at least one second cam tooth. 
     
     
       13. The combination starter-generator device of  claim 12 , wherein the at least one first cam tooth is radially and circumferentially offset relative to the at least one second cam tooth, and wherein the at least one second cam tooth is radially and circumferentially offset relative to the at least one third cam tooth. 
     
     
       14. The combination starter-generator device of  claim 13 ,
 wherein the first clutch includes a first ring base and at least one first clutch tooth extending from the first ring base, the second clutch includes a second ring base and at least one second clutch tooth extending from the second ring base, and the third clutch includes a third ring base and at least one third clutch tooth extending from the third ring base, and 
 wherein, in the respective engaged positions of the first, second, and third clutches, the at least one first tooth, the at least one second tooth, and the at least one third tooth are engaged with the gear set. 
 
     
     
       15. The combination starter-generator device of  claim 14 ,
 wherein the gear set includes a compound epicyclic gear train including an input shaft, first-stage and second-stage sun gears, first-stage and second-stage planet gears, first-stage and second-stage carriers, and a ring gear with the first-stage planet carrier splined to the second-stage sun gear, and wherein the first-stage planet gears have a different gear tooth count than the second-stage planet gears; 
 wherein, in a cold engine start mode, the first clutch is in the engaged position to ground the second-stage planet carrier and the second and third clutches are in the disengaged positions, and further, rotational power from the electric machine moves in the first power flow direction from the input shaft, to the first-stage sun gear, to the first stage-planet gears, to the first-stage planet carrier, to the second-stage sun gear, to the second-stage planet gears, and to the ring gear out to the engine at the first gear ratio; and 
 wherein, in a warm engine start mode, the second clutch is in the engaged position to ground the second-stage sun gear and the first and third clutches are in the disengaged positions, and further, the rotational power from the electric machine moves in the first power flow direction from the input shaft, to the first-stage sun gear, to the first stage-planet gears, and to the ring gear out to the engine at the second gear ratio. 
 
     
     
       16. The combination starter-generator device of  claim 15 ,
 wherein, in a boost mode, the third clutch is in the engaged position to couple the second-stage sun gear to the first-stage sun gear and the first and second clutches are in the disengaged positions, and further, the rotational power from the electric machine moves in the first power flow direction from the input shaft, to the first-stage and second-stage sun gears, to the first-stage and second-stage planet gears, and to the ring gear out to the engine at the third gear ratio; and 
 wherein, in a generation mode, the third clutch is in the engaged position to couple the second-stage sun gear to the first-stage sun gear and the first and second clutches are in the disengaged positions, and further, rotational power from the engine moves in the second power flow direction from the ring gear, to the first-stage and second-stage planet gears, to the first-stage and second-stage sun gears, and to the input shaft out to the electric machine at the fourth gear ratio. 
 
     
     
       17. The combination starter-generator device of  claim 16 , wherein each of the third gear ratio and the fourth gear ratio is a 1:1 ratio through the gear set, and wherein the first gear ratio is greater than the second gear ratio, and the second gear ratio is greater than the third gear ratio. 
     
     
       18. A drivetrain assembly for a work vehicle, comprising:
 an engine; 
 an electric machine; 
 a gear set configured to receive rotational input from the electric machine and from the engine and to couple the electric machine and the engine in a first power flow direction and a second power flow direction, the gear set configured to operate in one of at least a first gear ratio, a second gear ratio, or a third gear ratio in the first power flow direction and at least the third gear ratio in the second power flow direction; 
 a clutch arrangement with at least one active clutch selectively coupled to the gear set to effect the first, second, and third gear ratios in the first power flow direction and the third gear ratio in the second power flow direction, wherein the clutch arrangement further includes at least one drag clutch to apply a drag force on the gear set to slow the electric machine; and 
 a cam plate configured to shift the at least one active clutch from a disengaged position in which the at least one active clutch is decoupled from the gear set into an engaged position in which the at least one active clutch is coupled to the gear set. 
 
     
     
       19. The drivetrain assembly of  claim 18 ,
 wherein the gear set includes an input shaft that receives the rotational input from the electric machine in the first power flow direction and an output element rotating with the engine, and 
 wherein the at least one drag clutch includes a first portion mounted on the input shaft and a second portion mounted for rotation with the output element that frictionally engage one another to apply the drag force. 
 
     
     
       20. The drivetrain assembly of  claim 19 , wherein the drag force is approximately 10 Nm.